The present invention relates to an inspection apparatus for a semiconductor defect and particularly to an inspection apparatus for a defect such as a precipitated particle or a stacking fault in a silicon wafer.
As the integration of a LSI (large scale integrated circuit) is being increased, decrease in a conforming item acquisition ratio and decrease in reliability caused by a failed MOS (metal oxide semiconductor) transistor composing the LSI becomes a large problem. As causes of the failed MOS transistor, dielectric breakdown of a gate oxide film and excessive leak current in a junction are typical problems. It is not preferable that a crystal defect is formed in a surface area having elements on a silicon wafer because a failed MOS transistor occurs, as described above.
Therefore, defect measurement is important in the quality control of silicon crystal. In regard to the method measuring such a defect, there is a method in which an infrared ray transmissible through the silicon is irradiated and the scattered light is detected. In such a measuring method, it is necessary to measure defect sizes and defect positions in the depth direction. This is because an effect of defect on the device differs depending on the defect size and the defect position in the depth direction. A technology to observe crystal defects is described in "Extended Abstracts of the 1996 International Conference on Solid State Devices and Materials, pages 151-153" and "Applied Physics, Vol. 65, No. 11 (1996)", pages 1162-1163.
In this technology, a light beam composed of two wavelengths of which absorptivities are different from each other by one digit is irradiated onto a wafer surface, and intensity of the scattered light from a defect is measured for each of the wavelengths to obtain a position of the defect in the depth direction and a dimension of the defect. The paper discloses a planar distribution diagram of defects inside a wafer detected by the technology, a display having depth from the surface in the abscissa and number of defects in the ordinate, and a distribution diagram having distance toward the radial direction from the center of a wafer in the abscissa and defect size in the ordinate. Defect inspection is performed to obtain the distribution diagrams and the displays described above, and to specify the distribution of defects existing on the surface of a wafer and inside the wafer and the trend of the defect production. It is well known that when very small stacking faults among the crystal defects are produced in an active region of a device, the characteristic of the device is hurt such as by increasing of the leak current.
Further, it is reported that the withstanding voltage characteristic of an initial oxide film strongly depends on a crystal pulling-up speed at crystal growth. This shows that a grown-in defect existing in the crystal just after crystal growth affects the electric characteristic.